1. Field of the Invention
The present invention relates to a method of transmitting and receiving a radio wave by rotating a plane of polarization of the radio wave.
2. Related Art Statement
The present invention is applicable to various fields such as electrical communication engineering, electronics engineering, radio wave propagation, radio communication equipment engineering, antenna engineering and information engineering. More specifically, the present invention may be applied to the following fields:
(1) data transmission between different stairs in a tall building (mutual connection of computers, E-mail and LAN), PA1 (2) data transmission over handy type transmitter and receiver between a fold in a ship and a land office; PA1 (3) data communication between transshipments (container crane and office of loading and unloading company) on land and officer's cabin in a ship; PA1 (4) guides for various kinds of robots by radio waves (collection of data from industrial robot, dam and weather monitoring equipment); PA1 (5) transmission of command for unmanned flying object and artificial satellite; PA1 (6) telemetry from monitoring satellite and information transmission media; PA1 (7) digital communication for high speed moving objects; PA1 (8) digital telecommunication (including broadcasting). PA1 radio wave of a carrier signal is transmitted from two dipole antennas which are mutually crossed at right angles and are arranged in a plane perpendicular to a propagating direction of the radio wave under such a condition that a plane of polarization of the radio wave is rotated in accordance with the digital signal to be transmitted, and PA1 the radio wave transmitted from said pair of dipole antennas is received by an antenna and the rotation of the plane of polarization of the received radio wave is detected to reproduce the digital signal. PA1 said transmitter comprises first and second dipole antennas being crossed each other by right angles and arranged in a plane perpendicular to a propagating direction of radio wave, and means for modulating a rotation of a plane of polarization of radio wave transmitted from said dipole antennas in accordance with a digital signal to be transmitted at one or more frequencies which are higher than a fading frequency, and PA1 said receiver comprises an antenna for receiving the radio wave transmitted by said dipole antennas of the transmitter, and means for detecting the rotation of the plane of polarization of the received radio wave to reproduce the digital signal. PA1 a first oscillator for generating a carrier signal having a first frequency; PA1 a second oscillator for generating a modulating signal having a second frequency which is lower than said first frequency of the carrier signal; PA1 a control circuit for receiving a digital signal in the form of a bivalent signal to be transmitted and generating a control signal having first and second values corresponding to two states of the digital signal; PA1 a first balanced modulator for modulating said carrier signal with a modulating signal generated from said second oscillator to produce a first balanced-modulated signal when said control signal has the first value; PA1 a 90.degree. phase shifter for shifting a phase of said modulating signal by 90.degree. to produce a phase shifted modulating signal; PA1 a second balanced modulator for modulating said carrier signal with said phase shifted modulating signal produced from said phase shifter to generate a second balanced-modulated signal shows phase is shifted by 90.degree. with respect to said first balanced-modulated signal; and PA1 first and second dipole antennas for transmitting said first and second modulated signals, respectively as radio waves a plane of polarization of composed radio waves is rotated when said control signal has the first value and is not rotated when the control signal has the second value, said first and second dipole antennas being crossed each other by right angles and being arranged in a plane perpendicular to a propagating direction of the radio wave. PA1 a first oscillator for generating a carrier signal; PA1 a control circuit for receiving a digital signal in the form of a bivalent signal to be transmitted and generating a control signal having first and second values corresponding to two states of the digital signal; PA1 a second oscillator for receiving said control signal and generating first and second modulating signals having first and second modulation frequencies when said control signal have the first and second values, respectively, said first and second modulation frequencies being lower than a frequency of said carrier signal; PA1 a first balanced modulator for modulating said carrier signal with the first or second modulating signal generated from said second oscillator to produce a first balanced-modulated signal; PA1 a 90.degree. phase shifter for shifting a phase of said first or second modulating signal by 90.degree. to produce a phase shifted modulating signal; PA1 a second balanced modulator for modulating said carrier signal with said phase shifted modulating signal produced from said phase shifter to generate a second balanced-modulated signal whose phase is shifted by 90.degree. with respect to said first balanced-modulated signal; and PA1 first and second dipole antennas being crossed each other by right angles and being arranged in a plane perpendicular to a propagating direction of the radio wave, and transmitting said first and second balanced-modulated signals, respectively as radio waves such that a plane of polarization of composed radio waves is rotated at the first modulation frequency when said control signal has the first value and is rotated at the second modulation frequency when said control signal has the second value.
Heretofore, the radio communication has been carried out by using the amplitude modulation, frequency modulation, phase modulation and combinations thereof. However, radio communications using the known modulation system is subjected to the influence of fading and noise. Because such influence could not be removed completely, it has been considered that the fading is caused by the change in the transmission medium which could not be controlled at all.